They're a great midwater fish. Very active and compared to the other Brycon species, the Hilarii are significantly more sociable. If you have the space, a shoal of 3-4 Hilarii (at 15-18" a piece) they would be a great addition to a large South American community. I think of them as a Vegan Dorado; belligerent but meek enough that they won't do any damage. Every now and again, my big one has a spat with the Gold Wolves but nothing more than excited circling in the middle of the tank, with the wolves gills flared.